1. Field of the Invention
The invention relates to a device for the production of an optical waveguide preform, and more particularly, to a device for forming a preform from a crude preform rod of quartz glass and at least one quartz glass tube fused thereto. The device consists of a glass lathe in which jaw chucks for the rotatable support of the crude preform rod and of the quartz glass tube are provided in the headstock.
2. Description of the Prior Art
A device of this type is known from German Patent No. 33 15 156. In the known device, the crude preform rod and the quartz glass tube slid over this are clamped at the same end into separate jaw chucks in the headstock of the glass lathe. The fusion of the quartz glass tube onto the crude preform rod is carried out by the fact that a gas burner is led along the rod-tube unit, starting from the unclamped end, while the unit rotates.
When using the known device, it has now been found that the crude preform rod moves away from the joint axis of symmetry of the rod and tube during fusion of the tube. However, this leads to the fact that an optical waveguide drawn from an optical waveguide preform of this type shows an inadmissibly large core eccentricity. Only very narrow tolerances are permitted in the core eccentricity of optical waveguides, because these cause a large attenuation at splice points or in optical waveguide connectors. Furthermore, in the case of the known device, it is not possible to accelerate the production of the optical waveguide preform by the establishment of a vacuum between the crude preform rod and the quartz glass tube.